Newly developed equipment such as electronic or automated anti-lock braking systems, stability control systems and regenerative braking systems have created a need for high performance hydraulic fluids (e.g., brake fluids) having appropriate physical and performance properties. In particular, there is a strong demand for high performance brake fluids having high equilibrium reflux boiling point (ERBP) and high Wet ERBP (WERBP) and low kinematic viscosity at −40 C, while maintaining or improving elastomer (Styrene Butadiene Rubber (SBR) cup) compatibility.
U.S. Pat. No. 6,558,569B1 describes brake fluids made using borate esters, alkoxy glycols and additives. U.S. Pat. No. 3,925,223 describes hydraulic fluids having improved wet equilibrium boiling points and improved rubber swell per FMVSS 116 using borate esters.
From the above, it would be desirable for a performance (e.g. brake) fluid that solves one or more of the deficiencies of the prior art such as described above and provide a fluid composition exhibiting desired properties in terms of high ERBP and high Wet WERBP) and low kinematic viscosity at −40 C, and low SBR cup volume swell.